12,299 research outputs found
Symmetry-guided nonrigid registration: the case for distortion correction in multidimensional photoemission spectroscopy
Image symmetrization is an effective strategy to correct symmetry distortion
in experimental data for which symmetry is essential in the subsequent
analysis. In the process, a coordinate transform, the symmetrization transform,
is required to undo the distortion. The transform may be determined by image
registration (i.e. alignment) with symmetry constraints imposed in the
registration target and in the iterative parameter tuning, which we call
symmetry-guided registration. An example use case of image symmetrization is
found in electronic band structure mapping by multidimensional photoemission
spectroscopy, which employs a 3D time-of-flight detector to measure electrons
sorted into the momentum (, ) and energy () coordinates. In
reality, imperfect instrument design, sample geometry and experimental settings
cause distortion of the photoelectron trajectories and, therefore, the symmetry
in the measured band structure, which hinders the full understanding and use of
the volumetric datasets. We demonstrate that symmetry-guided registration can
correct the symmetry distortion in the momentum-resolved photoemission
patterns. Using proposed symmetry metrics, we show quantitatively that the
iterative approach to symmetrization outperforms its non-iterative counterpart
in the restored symmetry of the outcome while preserving the average shape of
the photoemission pattern. Our approach is generalizable to distortion
corrections in different types of symmetries and should also find applications
in other experimental methods that produce images with similar features
Microwave-controlled generation of shaped single photons in circuit quantum electrodynamics
Large-scale quantum information processors or quantum communication networks
will require reliable exchange of information between spatially separated
nodes. The links connecting these nodes can be established using traveling
photons that need to be absorbed at the receiving node with high efficiency.
This is achievable by shaping the temporal profile of the photons and absorbing
them at the receiver by time reversing the emission process. Here, we
demonstrate a scheme for creating shaped microwave photons using a
superconducting transmon-type three-level system coupled to a transmission line
resonator. In a second-order process induced by a modulated microwave drive, we
controllably transfer a single excitation from the third level of the transmon
to the resonator and shape the emitted photon. We reconstruct the density
matrices of the created single-photon states and show that the photons are
antibunched. We also create multipeaked photons with a controlled amplitude and
phase. In contrast to similar existing schemes, the one we present here is
based solely on microwave drives, enabling operation with fixed frequency
transmons
Simplified normal forms near a degenerate elliptic fixed point in two-parametric families of area-preserving maps
We derive simplified normal forms for an area-preserving map in a
neighbourhood of a degenerate resonant elliptic fixed point. Such fixed points
appear in generic two-parameter families of area-preserving maps. We also
derive a simplified normal form for a generic two-parametric unfolding. The
normal forms are used to analyse bifurcations of -periodic orbits. In
particular, for we find regions of parameters where the normal form has
"meandering'' invariant curves
Determination of the domain of the admissible matrix elements in the four-dimensional PT-symmetric anharmonic model
Many manifestly non-Hermitian Hamiltonians (typically, PT-symmetric complex
anharmonic oscillators) possess a strictly real, "physical" bound-state
spectrum. This means that they are (quasi-)Hermitian with respect to a suitable
non-standard metric. The domain D of the existence of this metric is studied
here for a nontrivial though still non-numerical four-parametric "benchmark"
matrix model.Comment: 18 pages, 2 figure
- âŠ